How to roll the viewport?
You can press &#9096; Ctrl&#8679; Shift ScrollWheel, or &#8679; ShiftNumpad 4 and &#8679; ShiftNumpad 6.



Currently the scrollwheel binding doesn't exist in 2.8, however you can add it back yourself. Under User Preferences > Input > 3D View > 3D View (Global), press Add New and set the operator to view3d.view_roll. Create a binding for both left and right: